Method of implanting the tibial augment

ABSTRACT

A tibial augment for use with a knee joint prosthesis, composed of annular members of different stock sizes, each size being configured to fit within a cavity formed in a human tibia. The augment may include a stepped distal surface. A provisional (temporary) tibial augment used to ensure a proper fit for the permanent augment is also provided. The provisional may include grooves configured to cooperate with a set of ribs on a tong-like holder used for removing the provisional from the cavity. A pusher for use implanting the tibial augment is also provided. In addition, a system for creating a cavity in a human tibia is also described. The system preferably includes a guide with a slot therein and a set of osteotomes that are inserted within different portions of the slot. Methods for using the tools and/or implanting the prosthetic devices discussed above are also described.

This application is a continuation of U.S. application Ser. No.12/886,297, filed Sep. 20, 2010, now issued as U.S. Pat. No. 8,506,645,which is a continuation of U.S. application Ser. No. 10/780,378, filedFeb. 17, 2004, now abandoned, which is a continuation-in-part of priorapplication Ser. No. 10/225,774, filed Aug. 22, 2002, now abandoned,which claims the benefit of Provisional Application No. 60/315,148,filed Aug. 27, 2001, each of which are hereby incorporated by reference.

The present invention relates generally to a bone augmenting member usedto reinforce damaged bone, and more particularly to an augment for theproximal portion of a human tibia, where the augment is intended to beimplanted in the proximal portion of the tibia, just slightly below thetibial portion of a knee joint prosthesis. The present invention alsorelates to the tool used for implanting the tibial augment, and thetools used for making the cavity in the bone to receive the augment. Inaddition, the invention also relates to a provisional augment usedtemporarily to ensure that the permanent augment will be seated withinthe bone correctly, as well as to a holder used for holding, insertingand removing the provisional augment.

BACKGROUND OF THE INVENTION

Knee replacement surgery methods and knee joint prostheses are known inthe art. A typical knee joint prosthesis includes a rounded femoralcomponent that is attached to the distal portion of the femur, and atibial component, which may be formed of a single piece or from twoseparate pieces that are joined together, that is attached to theproximal portion of the tibia. The femoral component rides on theexposed surface of the tibial component, replicating natural kneemovement as closely as possible. When such knee replacement surgery isperformed, an incision is made to expose the knee joint in order toenable removal of both the proximal portion of the tibia and the distalportion of the femur, which creates surfaces upon which the tibial andfemoral components of the knee prosthesis can be attached.

In certain situations, additional portions of the tibia, other than therelatively narrow proximal portion being removed during knee replacementsurgery, may also be damaged by arthritis or other problems. In suchsituations, a relatively thick proximal portion of the tibia is oftenremoved, and it is replaced with an augment block shaped like the bonethat has been removed. However, such previously known methods oftenresult in the removal of an unnecessary amount of healthy bone, alongwith the damaged bone. Thus, for example, even in cases where theperipheral bone was healthy, and only the internal bone was damaged,prior art methods often removed both the healthy peripheral bone and thedamaged internal bone

BRIEF SUMMARY OF THE INVENTION

The present invention is intended for situations in which the proximalportion of the tibia is defective, and it provides a method and devicesthat allow for preservation of healthy peripheral bone, while stillproviding the necessary augmentation to the proximal portion of thetibia. Preservation of the healthy peripheral bone provides for earlyonset of bony ingrowth into the tibial augment and allows the bone toinfiltrate the augment, restoring the bony platform upon which otherimplants can reside.

More specifically, the present invention provides a tibial augment foruse with a knee joint prosthesis that is made of an annular member witha proximal surface, a distal surface, an outer anterior surface, aninner anterior surface, an outer posterior surface, an inner posteriorsurface, an inner lateral surface, an outer lateral surface, an innermedial surface and an outer medial surface. Preferably, the outerlateral surface is curved to define a continuous surface connecting theouter posterior surface and the outer anterior surface; and the outermedial surface is also curved to define a continuous surface connectingthe outer posterior surface and the outer anterior surface. In addition,the outer anterior surface is slightly curved and the outer posteriorsurface is a generally planar surface. The annular member can be made ina variety of different stock sizes, with each size being configured tofit within a cavity formed in a proximal portion of a different sizedhuman tibia.

In certain embodiments, the tibial augment of the present invention caninclude a stepped distal surface, thereby defining a first distalsurface and a second distal surface with a transition surfacetherebetween, where the first distal surface is located at a greaterdistance from the proximal surface than the second distal surface. Thetransition surface can be located at different portions of the augment,such as: (1) midway between the outer lateral surface and the outermedial surface; (2) closer to the outer lateral surface than to theouter medial surface; or (3) closer to the outer medial surface than tothe outer lateral surface.

The present invention also includes a provisional or temporary tibialaugment that is used to ensure a proper fit for the permanent augment.The provisional augment is preferably composed of a material that issubstantially transparent to allow visualization of the bony contactsurfaces that will likely contact the augment. In addition, in thepreferred embodiment, the provisional augment preferably includes atleast one set of generally lateral/medial extending grooves tofacilitate removal of the provisional from the cavity formed in thetibia. The grooves are configured to cooperate with a set of ribs on atong-like holder used for inserting and removing the provisional fromthe cavity.

The present invention also relates to a pusher for use in implanting thetibial augment, where the pusher includes a handle portion and anaugment seating portion. The augment seating portion is connected to oneend of the handle portion, and is configured and arranged to seat aparticularly sized tibial augment.

In addition, the present invention also relates to a system used forcreating a cavity in a proximal portion of a human tibia for use priorto implanting a knee joint prosthesis. The system preferably includes aguide with a slot therein and a set of osteotomes that are configuredand arranged to be inserted within different portions of the slot on theguide.

Additionally, the present invention also relates to a holder forinserting and/or removing a provisional augment to/from a cavity in abone. The holder preferably includes a body portion, a pair of legsextending from the body portion, a finger connected to each of the legs,and a rib extending outwardly from each of the fingers. Each of the ribspreferably extends in a direction that is generally perpendicular to thelongitudinal axis of the body portion, and the ribs are configured andarranged to correspond to grooves on an inner surface of a provisionalaugment. In a first preferred embodiment of the holder, the pair of legscomprises a pair of flexible legs, such that application of a force uponouter surfaces of the legs allows for the ribs to be disengaged from thegrooves on the inner surface of the provisional augment withoutsignificantly altering the location of the provision augment. In thesecond preferred embodiment of the holder, each of the legs is arelatively rigid member, and each of the fingers is attached to one ofthe legs such that the fingers are movable with respect to the legs,whereby movement of the fingers with respect to the legs allows for theribs to be disengaged from the grooves on the inner surface of theprovisional augment without significantly altering the location of theprovision augment. The second embodiment of the holder is alsopreferably adjustable to permit a single holder to be used withprovisional augments of different sizes.

The present invention also relates to the methods of using the toolsand/or implanting the prosthetic devices discussed above.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention are described herein withreference to the drawings wherein:

FIG. 1 is a perspective view of a preferred embodiment of a tibialaugment of the present invention;

FIG. 2 is a top view of the tibial augment of FIG. 1;

FIG. 3 is an anterior view of the tibial augment of FIG. 1, with theposterior view being identical due to symmetry along the major axis;

FIG. 4 is a lateral view of the augment of FIG. 1, with the medial viewbeing a mirror image thereof;

FIG. 5 is a perspective view of a tibial augment of a different heightthan that shown in the FIG. 1 embodiment;

FIGS. 6A-6C are anterior views of three different stepped versions ofthe tibial augment of the present invention;

FIG. 7 is a view of a tibia, shown with the damaged proximal bonesurface removed and also including a cavity within which a tibialaugment of the present invention will be implanted;

FIG. 8 is a view of a tibial augment of the present invention, shownimplanted in place below a knee joint prosthesis;

FIG. 9 is a perspective view of a provisional tibial augment of thepresent invention;

FIG. 10 is a top view of a holder of the present invention, where theholder is intended for use with the provisional of FIG. 9;

FIG. 11 is a side view of the holder of FIG. 10;

FIG. 12 is a perspective view of a second embodiment of a holder of thepresent invention;

FIG. 13 is a front view of the holder of FIG. 12;

FIG. 14 is a perspective view of a pusher of the present invention,which pusher is intended to be used to implant the tibial augment;

FIG. 15 is a bottom view of the pusher of FIG. 14;

FIG. 16 is a side view of the pusher of FIG. 14;

FIG. 17 is a front view of the pusher of FIG. 14, and an enlarged viewof the augment seating portion upon which a tibial augment has beenseated;

FIG. 18 is a perspective view of a guide and a curved osteotome of thepresent invention, which are used for making a cavity for the augment;

FIG. 19 is a bottom view of the guide of FIG. 18;

FIG. 20 is a side view of the guide of FIG. 18;

FIG. 21 is a side view of the osteotome of FIG. 18;

FIG. 22 is a rear view of the osteotome of FIG. 18;

FIG. 23 is a bottom view of the osteotome of FIG. 18;

FIG. 24 is a bottom view of the osteotome of FIG. 25;

FIG. 25 is a perspective view of the guide of FIG. 18, shown with asecond osteotome of the present invention;

FIG. 26 is a perspective view of the guide of FIG. 18, shown with athird osteotome of the present invention;

FIG. 27 is a side view of the osteotome of FIG. 26; and

FIG. 28 is a rear view of the osteotome of FIG. 26.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1 through 4, a first embodiment of the tibial augmentof the present invention is shown. The tibial augment is preferably anannular member 10, and it is preferably made from a tantalum basedporous material, such as Trabecular Metal™. Trabecular Metal™ isdesirable because it resembles bone and approximates the physical andmechanical properties of bone better than other materials. Use of such ametal enables increased bonding with the adjacent bone by allowing thebone to grow into its highly porous surface. The tibial augment may alsobe made of other materials, and it is preferably made of a material thatfacilitates bony ingrowth.

The tibial augment 10 is anatomically sized and shaped to fill anexisting cavitary defect within the proximal human tibia or a cavityprepared in the proximal portion of a human tibia. In the preferredembodiment, a system of different stock sizes of augments would beavailable, as discussed more fully below, with different sizes beingused for different sized tibias. Further, if desired two augments ofdifferent sizes may be stacked upon each other if such stacking isnecessary to fill the cavity.

As shown in FIGS. 1 through 4, the tibial augment 10 includes a proximalsurface 12, a distal surface 14, an outer anterior surface 16, an inneranterior surface 18, an outer posterior surface 20, an inner posteriorsurface 22, an inner lateral surface 24, an outer lateral surface 26, aninner medial surface 28 and an outer medial surface 30. Of course,depending on which tibia (right or left) the augment is being implantedinto, the surfaces designated as the medial and lateral surfaces will bereversed. However, since the augment is symmetric with respect to itslateral and medial sides, such distinctions are irrelevant, and theterms lateral and medial are being used for convenience of descriptiononly.

To mimic the portion of the tibia bone that the tibial augment is beingimplanted into, the outer lateral surface 26 is curved to define acontinuous surface that connects the outer posterior surface 20 and theouter anterior surface 16. Likewise, the outer medial surface 30 iscurved to define a continuous surface that connects the outer posteriorsurface 20 and the outer anterior surface 16. The outer anterior surface16 is slightly curved and the outer posterior surface 20 is a generallyplanar surface.

As best shown in FIGS. 2 through 4, a majority of the annular member 10is of a substantially uniform thickness, as most readily depicted by thehidden lines of FIGS. 3 and 4. The major exception to the uniformthickness is a channel 32, shown in FIGS. 1 and 2, which defines areduced thickness portion. In the preferred embodiment, the thickness ofthe majority of the augment is preferably approximately 5 mm thick, andthe thickness of the reduced thickness portion is preferablyapproximately 3 mm at its narrowest point. However, other dimensions arealso contemplated as being within the scope of the invention. Althoughthe preferred embodiment includes walls of a substantially uniformthickness, with a reduced thickness portion near channel 32, it is alsocontemplated that the walls could be tapered, in either direction,between the proximal and distal surfaces.

The reduced thickness portion is preferably included to provide a spacefor the stem of a stemmed tibial base plate of a knee joint prosthesis.One example of such a stemmed tibial base plate is shown in FIG. 8,which shows a knee joint prosthesis 100 that includes stemmed tibialbase plate 102 with a stem 104 extending through the tibial augment 10.FIG. 8 also shows a tibial articulating surface 106 and a femoralcomponent 108, which are also parts of the knee joint prosthesis 100.Although the present augment 10 is shown and described for use with astemmed tibial base plate and includes a channel for accommodating thebase plate's stem, it is contemplated that the present invention couldalso be used with other forms of base plates without stems, andtherefore the channel could be omitted. Further, it is also contemplatedthat the inner surfaces of the tibial augment of the present inventioncould be modified to accommodate other designs of tibial base plates,such as pegged base plate designs.

As shown in FIG. 3, both the outer medial surface 30 and the outerlateral surface 26 have a distal taper (i.e. downward slope) of betweenapproximately 8 degrees and approximately 30 degrees, with a taper ofapproximately 19 degrees being preferred. Such tapers replicate thetapers commonly found in corresponding areas of the proximal portions ofhuman tibias. Since the thickness of the annular member 10 is generallyuniform from its proximal side to its distal side, the inner medialsurface 28 and the inner lateral surface 24 will also have the sametaper as the outer lateral and medial surfaces.

Referring now to FIG. 4, the outer posterior surface 20 has a distaltaper of less than approximately 17 degrees, with a taper ofapproximately 12 degrees being preferred. The outer anterior surface 16is an essentially normal surface relative to the proximal surface 12.Like the tapers of the lateral and medial surfaces, those of theanterior and posterior surfaces were also chosen to mimic the tapers ofthe appropriate portions of a human tibia. Once again, due to therelatively uniform thickness, the tapers of the inner posterior andanterior surfaces (22 and 18, respectively) will be the same as those ofthe corresponding outer posterior and anterior surfaces (20 and 16,respectively).

The present invention also comprises a system of a plurality ofdifferently sized augments that can be held on hand in order toaccommodate tibias of different sizes. It is contemplated that three orfour different sizes in the anterior/posterior-medial/lateral directionshould suffice for most applications. For example, the lateral/medialdimension could range from about 40 mm to about 80 mm, when measuredfrom its widest point (which is at the proximal surface). Thus, if foursizes were to be used, the lateral/medial dimension of the smallesttibial augment (at its widest point) would be 48 mm for an extra smallaugment, 52 mm for a small augment, 59 mm for a medium augment and 67 mmfor a large augment. Additionally, the anterior/posterior dimensioncould range from about 30 mm to about 40 mm, when measured from thewidest point in the anterior/posterior direction (which is at theproximal surface). Thus, the approximate minimum dimensions for extrasmall, small, medium, and large augments would be 33 mm, 34 mm, 36 m and38 mm, respectively.

Further two different heights of augments should be available, where theheight is measured from the proximal surface 12 to the distal surface14. In cases where the decay has only extended a small distance into thetibia, a shorter augment can be used than that needed where the decayhas extended to a greater depth of the bone. As a general rule, as muchhealthy bone should be preserved as possible. However, if the decay isrelatively deep, two augments of different sizes may be stacked uponeach other. For example, a small augment may be stacked upon an extrasmall augment; a medium augment may be stacked upon a small augment; ora large augment may be stacked upon a medium augment. Due to the shapesof the outer peripheries of the augments, stacking essentially createsextensions of the outer lateral, medial, posterior and anteriorsurfaces.

It is believed that two different heights should be sufficient to remedymost tibial bone decay situations that are suitable for correction byimplantation of a tibial augment. For example, augments could beavailable in 15 mm and 30 mm heights. However, more than two heights mayalso be produced, if desired. The tibial augment 10 shown in FIGS. 1through 3 is one example of an augment of the 30 mm height, and thetibial augment 40 shown in FIG. 5 is one example of an augment of the 15mm height. The augment 40 of FIG. 5 is essentially the same as theaugment 10 of FIGS. 1 through 4, except for the height thereof.Accordingly, the same index numbers have been used in FIG. 5 as thoseused in FIGS. 1 through 4.

In order to accommodate the requirements of most situations, multiplesizes and shapes of augments may be desired. In the preferred embodimentof a set of augments, six different sizes of augment are believed to besufficient—extra small, small, medium and large in a short height (suchas 15 mm) and medium and large in a tall height (such as 30 mm). Thus,in a system including these basic sizes, there is no tall height (suchas 30 mm) augments in the extra small size or the small size. It isbelieved that defective bone portions corresponding to these two sizesare better suited to be corrected by other methods.

Of course, all of the dimensions discussed above (and below) are beingprovided by way of example only, and other dimensions are alsocontemplated as being within the scope of the invention. However, thedimensions provided, as divided into four different increments, arebelieved to be able to accommodate the needs of the majority ofpatients. Accordingly, only a limited stock of differently sizedaugments would need to be kept on hand. Thus, for example, a kit ofaugments would only need to contain four different sizes of augments ofthe 15 mm height, and two different sizes of augments of the 30 mmheight.

Turning now to FIGS. 6A through 6C, three different stepped versions ofa tibial augment are shown. More specifically, FIG. 6A shows steppedaugment 50, FIG. 6B shows stepped augment 60 and FIG. 6C shows steppedaugment 70. Since only the distal surface of the stepped augments isdifferent from the augment of FIGS. 1 through 4, only that portion needsto be discussed. In addition, the same index numbers as those used inFIGS. 1 through 4 will be used for similar features found in FIGS. 6Athrough 6C.

FIG. 6A shows tibial augment 50, which includes a stepped distal surface14 a/14 b with a transition surface 52 therebetween. As shown in thefigure, distal surface 14 a is located at a greater distance from theproximal surface 12 than distal surface 14 b. In this embodiment, thetransition surface 52 is located approximately midway between the outermedial surface 30 and the outer lateral surface 26.

A second embodiment of a stepped tibial augment is shown in FIG. 6B, asrepresented by tibial augment 60. In this embodiment, as in the FIG. 6Aembodiment, distal surface 14 a is located at a greater distance fromthe proximal surface 12 than distal surface 14 b. The main differencebetween this embodiment and the FIG. 6A embodiment is the location ofthe transition surface 52. In this embodiment, the transition surface 52is located closer to the outer lateral surface 26 than to the outermedial surface 30.

FIG. 6C shows a third embodiment of a stepped tibial augment 70. In thisembodiment, as in the embodiments of FIGS. 6A and 6B, distal surface 14a is located at a greater distance from the proximal surface 12 thandistal surface 14 b. The main difference between this embodiment and theother two embodiments is the location of the transition surface 52. Inthis embodiment, the transition surface 52 is located closer to theouter medial surface 30 than to the outer lateral surface 26.

The embodiments of FIGS. 6A through 6C are especially useful where therehas been uneven tibial decay, i.e., where there is more decay on eitherthe lateral side or the medial side than on the other side. By using oneof the stepped tibial augments shown in FIGS. 6A through 6C, morehealthy bone, if it exists on one side or the other, can be preserved,and mostly only defective bone will end up being removed when forming astepped cavity to implant the tibial augment. In other words, the baseof the cavity into which the stepped tibial augment will be implantedwill be stepped to correspond to the stepped distal surface of theaugment. Such a stepped-base cavity provides for preservation of morehealthy bone on the shallower side, as compared with a flat-based cavitywhere bone has been removed to a depth equal to the depth of the lowestdamaged area of bone.

Suggested heights for the stepped tibial augments of FIGS. 6A through 6Care 15 mm and 30 mm (as measured from the proximal surface 12 to thedistal surfaces 14 b and 14 a, respectively). Of course, other heightsare also contemplated as being within the scope of the invention.

FIG. 7 shows an example of a human tibia 80 into which a cavity 82 hasbeen prepared or formed in a proximal portion thereof. The cavity 82 ofthis example has a flat base 84, so it is suitable for tibial augmentswith flat distal surfaces, such as those depicted in FIGS. 1 through 5.However, those of ordinary skill in the art should be able to adapt theflat base 84 into a stepped base using the cavity forming techniquesdescribed hereinbelow.

The tibia 80 of FIG. 7 is shown in a state prior to implantation of atibial augment and a knee joint prosthesis. More specifically, theextreme proximal portion of the tibia 80 has been removed. Normally,most, if not all, of the removed proximal portion will be damaged tibialbone. However, a small amount of healthy bone may also need to beremoved at the same time in order to provide a relatively flat surfaceupon which the flat-bottomed tibial base plate 102 (FIG. 8) can beseated.

Either prior to removing the extreme proximal portion 86, or immediatelyafter removing it (depending upon which surgical techniques are used),an intramedullary rod 88 may be inserted and used to define therelationship between the knee prosthesis stem and the tibial augment.

An example of a tibial augment 10 that has been implanted into a humantibia is shown in FIG. 8. This figure shows how the tibial augment 10that is seated within a cavity, such as cavity 82 of FIG. 7, ispositioned directly distal of the stemmed tibial base plate 102.Preferably, the tibial base plate 102 is cemented to the tibial augment10. The remainder of the components of the knee joint prosthesis 100(the articulating surface 106, the femoral component 108, etc.) are allimplanted in the customary manner. It should be noted that although onlyone form of knee joint prosthesis has been shown and described, thetibial augments of the present invention can be used with other types ofknee joint prostheses.

FIG. 9 shows an example of a provisional tibial augment 90, which is atemporary augment used as a test to ensure that the permanent augmentwill fit properly within the cavity. Although only one size provisionalis shown and described, provisional augments should be made tocorrespond to every size of tibial augment, including the steppedaugments. There are two main differences between the provisional augment90 and the permanent augments of FIGS. 1 through 6C.

First, the provisional augment 90 may be made of a material whichindicates the bony areas of the provisional so that the surgeon canvisualize how the augment fits within the cavity. For example, theprovisional may be made of a transparent or photo-elastic material. Oneexample of a suggested material for the provisional ispolyphenylsulfone, although other materials are also contemplated.

Second, provisional augments preferably include a set of grooves 92/94on the inner medial surface 28 and the inner lateral surface 24. Thesegrooves 92 and 94 extend in the generally lateral/medial direction, andare configured to cooperate with ribs 96 on holder 110 shown in FIG. 10.The holder 110 is designed to facilitate insertion and removal of theprovisional augment 90 to/from the cavity 82 (FIG. 7) in order todetermine that there is a proper fit between the cavity and theprovisional augment (and therefore there is necessarily a proper fitwith the permanent augment also, since both the provisional and thepermanent augment are the same size and shape).

The holder 110 includes two flexible legs 112 that extend in onedirection (to the left, as shown in FIGS. 10 and 11) to a body portion114 that is topped with a crown portion 116. As shown towards theright-hand sides of FIGS. 10 and 11, each leg 112 connects with ashoulder portion 118. Each shoulder portion 118 in turn extends into afinger portion 120, upon which the ribs 96 are situated. The lowermostsurfaces of the shoulders 118 each include a stop surface 122, which isused to align the holder 110 with the proximal surface 12 of theprovisional 90 (FIG. 9) to facilitate the mating of the ribs 96 of theholder 110 with the grooves 92 and 94 of the provisional 90.

The holder 110 is preferably made of stainless steel, but it iscontemplated that it may also be fabricated from plastic. A keyconsideration when selecting material is that the legs 112 must beflexible enough to be able to be biased inwardly towards each other withlight force applied from the surgeon's thumb and forefinger, but theymust also be resilient enough to return to their original positions whenthe force is removed.

In use, the legs 112 of the holder 110 are flexed inwardly by thesurgeon, and the fingers 120 are inserted into the interior of theprovisional 90 (which is an annular member). Once the stops 122 contactthe proximal surface 12 of the provisional, the ribs 96 of the holdershould be face to face with the grooves 92 and 94 of the provisional 90.Pressure on the legs 112 can now be released, and the legs 112 will flexoutwardly until the ribs 96 mate with the grooves 92 and 94. At thispoint, the holder 110 can be moved (such as by holding the crown portion116 and/or by the body portion 114), and the provisional 90 will remainattached to the holder 110, for inserting/removing the provisional 90to/from the cavity 82 (FIG. 7).

One important feature of the holder 110 is that it can be disengagedfrom the provisional without affecting the position of the provisional.Thus, once the provisional is seated in the desired position, the legs112 can be squeezed together, and the holder 110 can be removed withoutdisrupting the position of the provisional.

Only one size holder 110 has been shown, but it should be understoodthat since the ribs of the holder are specifically configured to makecontact with the grooves on the inner surfaces of a provisional tibialaugment, a different sized holder is necessary for each different sizedprovisional. However, since the grooves are near the proximal surface ofthe each provisional, no additional holder needs to be fabricated for aprovisional that has the same sized proximal surface as anotherprovisional. In the preferred set of augments and provisionals, thereare six basic sizes—(1) extra small with 15 mm height; (2) small with 15mm height; (3) medium with 15 mm height; (4) medium with 30 mm height;and (5) large with 15 mm height and (6) large with 30 mm height.However, in the preferred embodiment, the 30 mm height medium-sizedprovisional (or augment) is essentially a 15 mm height medium-sizedprovisional (augment) stacked upon a 15 mm height small-sizedprovisional (augment). Similarly, in the preferred embodiment, the 30 mmheight large-sized provisional (or augment) is essentially a 15 mmlarge-sized provisional (augment) stacked upon a 15 mm medium-sizedprovisional (augment). Thus, the 30 mm height medium-sized provisionalcan employ the same holder as the 15 mm medium-sized provisional (sincethey have the same proximal dimensions), and the 30 mm large-sizedprovisional can employ the same holder as the 15 mm large-sizedprovisional. Accordingly, in the preferred set of six differently sizedprovisionals, only four holders are utilized because one holder doesdouble duty for both the 30 mm medium provisional and the 15 mm mediumprovisional, and another holder does double duty for both the 30 mmlarge provisional and the 15 mm large provisional.

Further, if extra small, small, medium and large stepped provisionalsare also included, the number of holders does not need to be increasedbecause the rib spacing on a stepped provisional is the same as that ofa similarly sized flat-bottomed provisional. Thus, the extra smallholder can be used with the extra small stepped provisional, the smallholder with the small stepped provisional, the medium holder with themedium stepped provisional, and the large holder with the large steppedprovisional.

Turning now to FIGS. 12 and 13, a second embodiment of the holder willbe shown and described. The second embodiment of the holder, which willbe designated as holder 111, is adjustable so that it can be used withprovisionals of a variety of different sizes, as well as withprovisionals other than tibial augment provisionals, such as femoralprovisionals. Holder 111 includes a body portion 113 that serves as ahandle and may optionally include a ribbed surface 115 that allows for amore secure grip. The body portion 113, which defines a longitudinalaxis (a vertical axis as shown in FIGS. 12 and 13), is connected to apair of legs 117. These legs 117 are each preferably L-shaped, and arepreferably attached to the lower portion of the body portion 113 bywelding (although other attaching means, such as screws, may be usedinstead). On the other hand, if desired, the legs 117 and the bodyportion 113 may be formed as a single unit, such as by casting, whichwill eliminate the need for any attaching means for connecting the legswith the body portion. When viewed together, the body portion 113 andthe legs 117 define a generally fork-shaped component, as shown in FIG.13.

Each of the legs 117 includes a finger 119 connected thereto. Thefingers 119 are preferably connected to the legs 117 via an externallythreaded shaft 121. The threaded shaft 121 is divided in half such thatone half is threaded in one direction and the other half is threaded inthe opposite direction. Each of the fingers includes an internallythreaded aperture 123 that is configured to mate with the associatedportion of the threaded shaft 121. Thus, when knob 125 is turned in onedirection, the threaded shaft 121 will rotate within threaded apertures123, which will cause the fingers 119 to separate from each other, andwhen the knob is turned in the other direction, the fingers 119 willmove towards each other. For example, the threaded shaft 121 could beconfigured such that clockwise rotation of the knob 125 will cause thefingers 119 to move closer together and counterclockwise rotation willcause the fingers to move farther apart (or, if desired, it could beconfigured in the opposite manner, where clockwise rotation causesgreater separation and counterclockwise rotation reduces the separationdistance). As shown in FIG. 13, each of the fingers 119 preferablyincludes a thickened portion 129, which serves to increase the contactarea between the threaded aperture 123 and the threaded shaft 121.Thickened portions 129 also provide stops that prevent the fingers 119from coming too close together.

For the purpose of connecting the threaded shaft 121 to the legs 117,each of the legs preferably includes an open-ended slot 127 forreceiving the ends of the shaft, which are preferably not threaded.After one end of the threaded shaft 121 has been inserted into each slot127, a small metal block is welded to each slot to close its open-end,which serves to maintain the threaded shaft in position, while stillallowing rotation of the threaded shaft with respect to the legs. Ofcourse, other methods of attaching the threaded shaft 121 to the legs117 are also contemplated as being within the scope of the invention.

A secondary shaft 131 is also provided in parallel with the threadedshaft 121. The secondary shaft 131 is preferably not threaded, and isprovided in order to prevent the fingers 119 from rotating with respectto the legs 117 when the threaded shaft 121 is rotated. The fingers 119are connected to the secondary shaft 131 via a pair of apertures 133(where one aperture extends through each finger), which allows thefingers to slide along, as well as rotate with respect to, the secondaryshaft 131. Optionally, in order to alleviate possible binding as thefingers 119 travel along the secondary shaft 131, the secondary shaftmay be slightly tapered from the center thereof. For example, the centerportion 135 may be made of full diameter, and extending outwardlytherefrom towards the legs 117, the secondary shaft 131 may include aone degree taper (although tapers of different degrees may also beprovided), with the ends seated within apertures 133 preferably being ofthe same diameter as the center portion 135. Preferably, the secondaryshaft 131 is welded in place at the apertures 133, although other waysof attaching the secondary shaft to the legs may also be used.Additionally, other means of preventing the fingers 119 from rotatingwith respect to the threaded shaft are also contemplated as being withinthe scope of the invention. For example, the legs and/or the bodyportion may include some form of protrusion extending therefrom forpreventing rotation of the fingers 119 with respect to the legs 117, butwhich still permits the fingers to move sideways (i.e., towards and awayfrom each other) with respect to the legs. As another example, the upperportions of the fingers 119 may be configured to include forks thatextend upwardly to straddle the legs 117 and/or the lower portion of thebody portion 113.

Each of the fingers 119 also includes a rib 137, and they also eachpreferably include a stop surface 139. As with holder 110 of FIGS. 10and 11, the ribs 137 of holder 111 are configured to mate with thegrooves 92 and 94 of the provisional 90 (FIG. 9) for inserting andremoving the provisional to/from the cavity, and the stop surfaces 139are used to align the holder 111 with the proximal surface 12 of theprovisional 90 to facilitate mating the ribs of the holder with thegrooves of the provisional.

The holder 111 is preferably made of stainless steel or of anothermetal, but other materials may be used for all or for only some of thecomponents. For example, plastic may be used for certain parts such asthe body portion 113, the knob 125 and the secondary shaft 131, while ametal or other different material may be used for the remainingcomponents.

In order to accommodate many different sizes of tibial augmentprovisionals, as well other types of provisionals (such as femoralprovisionals), the spacing of the fingers 119 should be able to beadjusted so that the fingers are far enough apart to enable the ribs 137to engage with the grooves of the largest provisional, as well as to beadjusted to be close enough together for use with the smallestprovisional. For example, a distance of approximately two inches betweenthe outer surfaces of the fingers 119 when separated at the maximumdistance and a distance of approximately three quarters of an inch whenseparated at the minimum distance should be sufficient for most uses. Ofcourse, these dimensions are only provided as a suggestion, and otherdimensions may also be used.

In use, the knob 125 is rotated to separate the fingers 119 by adistance that is less than the distance that separates the grooves ofthe provisional being acted upon (such as grooves 92 and 94 ofprovisional 90 in FIG. 9). The stop surface 139 is positioned upon theproximal surface of the provisional, and the ribs 137 of the holder arealigned with the grooves 92 and 94 of the provisional 90 (FIG. 9). Theknob 125 is again rotated to make the ribs 137 engage the grooves 92 and92, and the provisional 90 is inserted into the cavity 82 (FIG. 7). Theholder 111 can be disengaged from the provisional 90 by rotating theknob 125 to bring the fingers 119 closer together, separating the ribs137 from the grooves 92 and 94. One important feature of the holder 111is that is allows the ribs to be disengaged from the grooves withoutsignificantly altering the location of the provisional within thecavity. When the provisional 90 is to be removed from the cavity 82, theholder 111 is again used in the manner described above.

The preferred embodiments of the provisional and holder combination havebeen shown and described with grooves on the inner lateral and medialsurfaces. However, it is also contemplated that the grooves could beplaced on the inner anterior and posterior surfaces, and that thespacing of the fingers on the holder could be adjusted accordingly.Further, detents could be substituted for the grooves, and a springloaded holder for mating with the detents could also be used.

It is also contemplated that other means for inserting the provisionalmay also be used. For example, the provisional may include a threadedcircular holder into which a threaded handle member can be inserted andremoved.

Turning now to FIGS. 14 through 17, these figures show an example of atibial augment pusher 130, which is used to seat a tibial augment withinthe cavity of the proximal portion of the tibia. The pusher 130 (or oneof the holders) may also be used in conjunction with the provisionaltibial augment as a tamp. In situations where a bone graft is necessaryto fill a void within the tibia in preparation for receiving theprovisional tibial augment within the cavity, the void could be filledwith morselized bone and the provisional tibial augment (in combinationwith a holder or pusher) could be used to tamp the morselized bone intoplace.

The pusher 130 includes a handle portion 132 and an augment seatingportion 134. The augment seating portion 134 is further divided into ahead portion 136 and a platform portion 138. The head portion 136 ispreferably shaped to mimic the interior surfaces of the tibial augment10 (FIG. 1), except the head portion 136 is slightly smaller than thecorresponding surfaces of the tibial augment 10 associated therewith,which permits the head portion 136 to be easily seated within (andeasily withdrawn from) the tibial augment 10. More specifically, thereis preferably approximately 0.030 inches (0.762 mm) clearance betweenthe outer surface of the head portion 136 and the inner surfaces of thetibial augment 10, as represented by distance “X” in FIG. 17, whichincludes (in the main view) a front view of pusher 130 and a magnifiedview of part of the head portion 136 of the same pusher, but with atibial augment 10 seated thereon. That is, the magnified view of FIG. 17shows the head portion 136 in hidden lines to represent that the headportion is hidden behind the augment 10, with the inner surface of theaugment (also in hidden lines) spaced from the outer surface of the headportion 136 by distance “X.”

As also shown in the magnified portion of FIG. 17, the proximal surface12 of the augment 10 contacts the planar surface 140 of the platformportion 138, which provides a surface from which the surgeon can applylight pressure to the augment 10 to align, locate, and to seat it withinthe cavity 82 (FIG. 7). As can be seen in FIGS. 16 and 17, the planarsurface 140 is provided upon the platform portion 138 at the interfacebetween the platform portion 138 and the head portion 136.

Since the shape of the head portion 136 mimics the shape of the interiorsurfaces of the augment 10, it follows that the head portion 136 shouldhave a taper of approximately 19 degrees (+/−3 degrees) at the surfacethat corresponds to the inner medial and lateral surfaces (as shown inFIG. 17), and that it should have a taper of approximately 12 degrees(+/−3 degrees) at the surface that corresponds to the inner posteriorsurface (as shown in FIG. 16). Further, as also shown in FIG. 16, thesurface of the head portion 136 that corresponds to the inner anteriorsurface is not tapered, but is instead substantially perpendicular tothe platform portion 138.

In order to properly orient a tibial augment 10 within a cavity, thepusher 130 must have a head portion 136 that is appropriately shaped, asdiscussed above, and the head portion must also be appropriately sized.Thus, as with the provisional holders 110 discussed earlier, a number ofpushers may be provided for the set of augments. For example, if thereare four sizes of augments (extra small, small, medium and large), withtwo heights available (15 mm and 30 mm) for the medium and the largesizes only, then there is a total of six differently sized augments.Accordingly, as with the provisional holders 110, there should also befour differently sized pushers—one pusher for the 15 mm extra smallaugment; one for the 15 mm small augment; one for the 15 mm mediumaugment, the 30 mm medium augment, and the medium stepped augments; andone for the 15 large augment, the 30 mm large augment, and the largestepped augments.

In its preferred form, each pusher 130 is preferably made with analuminum handle portion 132 and an acetyl seating portion 134. However,other materials can also be used. For example, the seating portion couldbe made from various polymers or metals and the handle portion could bemade of a different metal or from plastic.

Turning now to FIGS. 18 through 28, a guide and several associatedosteotomes that are all used to create a cavity in the tibia are shownand will be described next. One important aspect of the presentinvention is that the cavity formed in the tibia (such as cavity 82 ofFIG. 7) must be carefully created so that the tibial augment fits asprecisely as possible. Among the advantages of a precise fit is that themore precise the fit, the greater the stability of the implant.Accordingly, the present invention includes tools and a method ofcreating a cavity of the proper size and shape. Although only one methodof creating the cavity will be shown and described, other methods mayalso be used as a supplement to or in place of the method described. Forexample, a rasp technique may be used to either create the cavity or tomake fine adjustments to a cavity created by another method. With such atechnique, a rasp shaped like a tibial augment (with a rasp-like outersurface and a handle) is used to remove the bone and form the cavity (orto make fine adjustments to the shape of the cavity).

FIG. 18 shows a preferred embodiment of a guide 142 with a first curvedosteotome 144 inserted into a portion of a slot 146 formed within theguide 142. FIG. 25 shows a second curved osteotome 148 (inserted intothe guide 142), and FIG. 26 shows a straight osteotome 150 (alsoinserted into the guide 142). As the following description will show,all three different osteotomes (144, 148 and 150) are required to formthe cavity 82 (FIG. 7) because of the configuration of the slot 146,which is specifically configured to properly orient the osteotomes tocreate a cavity that corresponds to the tibial augment being implantedtherein. The osteotomes 144, 148 and 150 are preferably made ofstainless steel, although other materials are also contemplated.

As with several of the other components, the osteotomes and guides arepreferably configured in a variety of different sizes. In the preferredembodiment, there are four sets of osteotomes (extra small, small,medium and large) and four guides (extra small, small, medium, andlarge). As described more fully below, these four sets of osteotomes andfour guides can be used to create a cavity in the tibia for any of the15 mm, 30 mm or stepped augments of the preferred embodiment.

Turning first to FIGS. 18, 21 and 22, the first curved osteotome 144includes a handle 152 with a crown 154 at the top end thereof. Thecurved osteotome 144 also includes a cutting portion 156 attached to thehandle 152, and the cutting portion includes a tapered edge 158 at itsfar end and a plurality of first (or distal) stops 160 for hindering thecutting portion from extending into the slot 146 of the guide 142 past apredetermined distance. The cutting portion 156 of the osteotome 144also includes at least one second (or proximal) stop 162. As describedmore fully below, the slot 146 in the guide 142 preferably includes aplurality of cutouts 147 (FIG. 19), which allow the distal stops 160 topass through in order to use the proximal stop 162.

The proximal stop 162 is placed at a greater distance from the taperededge 158 than the distal stops 160, as can be seen in FIGS. 21 and 22.The use of such staggered stops allows a single osteotome to be used tomake two different cavities of two different depths, depending uponwhich stop is used and also depending upon which size guide is used.Thus, for example, assuming that tibial augments are provided in twodifferent heights (such as 15 mm and 30 mm), accommodations must be madeto provide cavities of two different depths (15 mm and 30 mm) so thatthe depth of the cavity coincides with the height of the tibial augmentbeing placed therein. When a shallow cavity is needed, the set ofosteotomes is inserted into the same sized guide (e.g., the set of smallosteotomes is used with the small guide, etc.) whereby the exteriorstops 160 contact a planar top surface 143 of the guide, hindering thecutting portion 156 from extending further into the guide, andaccordingly hindering further extension into the bone. By inserting theset of osteotomes into the same sized guide, distal stops 160 do notmate with cutouts 147, and therefore stops 160 do not pass throughcutouts 147. On the other hand, if a deep cavity is needed, the same setof osteotomes are inserted into the incrementally larger guide (e.g. thesmall osteotomes are used with the medium guide), whereby the distalstops 160 pass through cutouts 147 and the proximal stop 162 contactsthe planar top surface 143 of the guide, hindering the cutting portion156 from extending further into the guide, and accordingly hinderingfurther extension into the bone. The distal and proximal stops of theother osteotomes function in a similar manner. Although in the examplesprovided the distal and proximal stops have been shown and described asbeing on the radially exterior sides of the osteotomes, some or all ofthe stops may be provided on the radially interior sides of theosteotomes. Of course, if all stops are provided on the radiallyinterior sides of the osteotomes, then the cutouts 147 on the guide 142would have to be changed to be on the radially interior side of the slot146. Additionally, if the distal stops are provided on the radiallyexterior side of the osteotome and the proximal stops are provided onthe radially interior side (or vice versa), then the cutouts 17 could beomitted, if desired, as long as the slot was made wide enough to acceptthe cutting portion 156 including the stops.

As mentioned above, FIG. 25 shows an example of a second curvedosteotome 148. The second curved osteotome 148 is very similar to thefirst curved osteotome 144 in that it also includes a handle 164, acrown 166, and a cutting portion 168 with a tapered edge 170 and aplurality of distal stops 172, as well as at least one proximal stop174.

Although it appears as though the first curved osteotome 144 and thesecond curved osteotome 148 are identical to each other, but are justshown in different orientations, in actuality, they are mirror images ofeach other. More specifically, the front cutting area 176 of the firstcurved osteotome 144 and the front cutting area 178 of the second curvedosteotome 148 each have no inclination, which corresponds to the outeranterior surface 16 of the tibial augment 10 (FIG. 4) that also has noincline. Similarly, since the outer posterior surface 20 preferably hasan incline of approximately 12 degrees (although inclines within therange of between about 0 to about 17 degrees may also be used), as shownin FIG. 4, the posterior cutting area 184 of the first curved osteotome144 and the posterior cutting area 186 of the second curved osteotome148 is also provided with an incline of 12 degrees (or a correspondingincline within the range of about 0 to about 17 degrees, depending uponthe exact degree of incline provided to the anterior surface of thetibial augment). Likewise, the outer medial surface 30 and the outerlateral surface 26 of the tibial augment 10 are preferably inclined at19 degrees (or within the range of between about 8 to about 30 degrees),as shown in FIG. 3, the side cutting area 180 of first curved osteotome144 and the side cutting area 182 of second curved osteotome 148 arealso inclined at 19 degrees (or at whatever selected angle between 8 and30 degrees that the outer lateral and outer medial surfaces of theaugment are provided at). FIGS. 23 and 24 also show how cutting portion156 is a mirror image of cutting portion 168. Accordingly, the secondcurved osteotome 148 is not interchangeable with the first curvedosteotome 144.

FIGS. 26 through 28 show straight osteotome 150. Like the otherosteotomes, the straight osteotome includes a handle 188, a crown 190,and a cutting portion 192 with a tapered edge 194, distal stops 196, andat least one proximal stop 198. As shown in FIG. 27, the cutting portion192 is preferably inclined with respect to the handle. This degree ofincline corresponds to the degree of incline of the outer posteriorsurface 20 of the tibial augment 10 (FIG. 4). Thus, in the preferredembodiment, there is an incline of approximately 12 degrees. However,inclines of between approximately 0 degrees and approximately 17 degreesare also contemplated as being within the scope of the invention, aswell as other degrees of incline. The orientation of the cutting portion192 with respect to the handle 188 of this osteotome, as well as theother osteotomes, is intended to allow for the proper cutting angle whenthe handle is held perpendicular to the tibial surface within which thecavity 82 (FIG. 7) has been formed.

Moreover, as shown in FIGS. 18 through 20, 25 and 26, the guide 142 isalso provided so that the proper cutting orientation of the osteotomesis maintained, which thereby aids in making a cavity with sidewalls ofinclines that correspond to the inclines on the outer surfaces of thetibial augment. As mentioned earlier, the guide 142 includes a slot 146for guiding the cutting portions (156, 168, 192) of the osteotomes (144,148, 150). Each portion of the slot 146 is made with a particularincline that matches the incline of the corresponding outer surface ofthe tibial augment associated therewith. Thus, for example, as shown inhidden lines in FIG. 18, the slot's lateral portion 200 and the slot'smedial portion 202 are inclined, respectively, to match the slopes ofthe outer lateral surface 26 and the outer medial surface 30 of thetibial augment 10, which in the preferred embodiment is a 19 degreeincline. Likewise, the slot's posterior portion 204 and its anteriorportion 206 are also configured to correspond of the incline of,respectively, the outer posterior surface 20 and the outer anteriorsurface 16 of the tibial augment 10. Thus, in the preferred embodiment,the slot's posterior portion 204 will be inclined at approximately 12degrees and the slot's anterior portion 206 will have no incline.

The guide 142 also includes a securing arrangement that is used tosecure the guide to the bone within which the cavity is being formed.The securing arrangement includes an aperture 208 that is configured toreceive the intramedullary rod 88 (FIG. 7), which serves as both areference point for the guide and as the stable member that the guide issecured upon. The securing arrangement also includes a threaded hole 210(FIG. 18) that is configured to receive a setscrew 212 (FIG. 19), whichis comprised of a head 214 and a threaded shaft 216. Alternately, thesetscrew could also be replaced with a thumbscrew or the head could bereplaced with a lever or small handle to facilitate tightening withoutthe need for a screwdriver. The threaded hole 210 is preferably madewithin a collar 218, which allows for additional length of the setscrew212, and also allows for also easier access to the head of the setscrew,which may be necessary, especially if a thumbscrew of other similarcomponent is used in place of the setscrew.

The slot 146 of the guide 142 is not annular, but instead includes a gapnear its anterior portion 206, as best shown in FIG. 19. This gap iswhere the threaded shaft 216 of the setscrew extends through the guide.If this gap in the slot 146 were not present, there is a chance that thethreaded shaft 216 of the setscrew could accidentally be damaged if anosteotome were inserted into the slot at this area. Damaging thesetscrew could result in misalignment of the guide with respect to thebone, or it could make it difficult to remove the guide from theintramedullary rod 88.

With regard to sizing, there should be one guide and one set of threeosteotomes (two curved and one straight osteotome) for each 15 mm sizedtibial augment. Further, additional guides and osteotomes need not beprovided for the 30 mm sized or for the stepped augments. Thus, if foursizes of augments (extra small, small, medium and large) are provided,there should be four different sizes of guides and four sets ofosteotomes, with three osteotomes in each set, for a total of twelvedifferent osteotomes. To make cavities for any of the 15 mm augments,the same sized set of osteotomes and guide are used. For example, tomake a cavity for a 15 mm extra small augment, the extra small set ofosteotomes and the extra small guide is used. However, to make a cavityfor one of the 30 mm augments, the same sized guide is used, but the setof osteotomes for the next smaller size is used. For example, to make acavity for a 30 mm medium augment, the medium guide is used along withthe small set of osteotomes. In other words, no matter what depth cavityis being created (15 mm or 30 mm), the guide that is the same size asthe augment being inserted (extra small, small, medium or large) willalways be used. However, when 30 mm depth cavities are being created,the set of osteotomes of one size smaller than the augment are used,otherwise (for 15 mm depth cavities), the set of osteotomes of the samesize as the augment are used.

To further clarify this point, the following specific examples areprovided. Assume that one intends to prepare a cavity suitable for themedium sized augment (of either 15 mm height or 30 mm height). First,for either case (15 mm or 30 mm), the medium sized guide 142 is affixedto the intramedullary rod 88. For creating a 15 mm depth cavity for themedium augment, medium osteotome 144 is inserted into thecorrespondingly sized medium guide, whereby the distal stop 160 contactsthe planar top surface 143 of the guide, hindering the cutting portion156 from extending further into the guide, past the desired 15 mm depth.The other medium osteotomes are also used in the same manner, with thestops operating in a similar manner to create a 15 mm depth cavity forthe 15 mm medium augment.

To create a 30 mm depth cavity for the 30 mm medium augment, the set ofsmall osteotomes (i.e., the osteotomes of one incremental size smallerthan the augment) would be inserted into the appropriate position of theslot 146, instead of using the medium osteotomes discussed above. Whensmall osteotome 144 is appropriately inserted into the incrementallylarger medium guide, the distal stop 160 passes through the medium guidecutout 147, allowing the cutting portion 156 of the osteotome to extendfurther into the bone until the proximal stop 162 contacts the planartop surface 143 of the guide. The contact of the proximal stop 162 withthe top planar surface hinders the cutting portion from extendingfurther into the guide than the desired 30 mm, and accordingly hindersfurther extension into the bone. (On the other hand, if small osteotome144 is inserted into the correspondingly sized small guide, the distalstop 160 contacts the planar top surface 143 of the guide, hindering thecutting portion of the 156 from extending further into the guide so thata 15 mm deep cavity can be created). The distal and proximal stops ofthe other small osteotomes function in a similar manner, and a 30 mmdepth cavity for the medium augment is created by using all three smallosteotomes with the medium guide.

To form a cavity in the proximal portion of the tibia, an appropriatelysized guide 142 and an appropriately sized set of osteotomes areselected. After the intramedullary rod 88 (FIG. 7) has been implantedwithin the tibia 80, the aperture 208 of the guide 142 is slid over theintramedullary rod 88, and the guide 142 is secured in place bytightening the setscrew 212. It should be noted that the aperture 208 ispreferably triangular, as best shown in FIG. 19, which allows for theintramedullary rod 88 to have an increasingly secure fit as the setscrewis tightened because of the way the rod is seated at the apex of thetriangle.

Once the guide 142 is securely attached to intramedullary rod 88, one ofthe appropriately sized osteotomes, such as the first curved osteotome144, is inserted into the appropriate position of the slot 146. Morespecifically, the first curved osteotome 144 is inserted into portion200 of the slot 146. It should be noted that the osteotomes may be usedin any desired order.

As discussed above, the desired depth of cavity is formed by using theappropriate combination of a particularly sized set of osteotomes withan appropriately sized guide, whereby either proximal stops 198 ordistal stops 196 are utilized to result in a cut of an appropriatedepth. Also, if one of the stepped tibial augments shown in FIGS. 6Athrough 6C is intended to be implanted, cuts of one depth may be made atone area of the cavity and cuts of another depth may be made at anotherarea in order to form an appropriate cavity with a stepped bottom toaccommodate the stepped distal surface 14 a/14 b of FIGS. 6A through 6C.

Next, one of the other osteotomes, such as the straight osteotome 150(FIGS. 26-28), is inserted into the appropriate portion of the slot. Asshown in FIG. 26, the straight osteotome 150 is inserted into the slot'sposterior portion 204 (best seen in FIG. 19). As described above, theappropriate stop, or stops, (either proximal stop 198 or distal stops196) is/are utilized to result in a cut of the appropriate depth.

Finally, the remaining osteotome, which in this case is the secondcurved osteotome 148 (FIG. 25), is inserted into the appropriate portionof the slot 146, which in this case is the medial portion 202 (FIG. 19).As with the other osteotomes, the appropriate stop, or stops, (eitherproximal stop 174 or distal stops 172) is/are utilized to result in acut of the appropriate depth. After all three osteotomes have been used,the guide 142 may be removed from the intramedullary rod 80 by looseningthe setscrew 218 and sliding the guide upwardly and off of theintramedullary rod. At this point, the bone to be removed should be cutto the desired depth, and it merely needs to be taken from the site toform the cavity 82 (FIG. 7). If necessary, an additional cut may need tobe made with the straight osteotome 150, or one of the other osteotomes,at the area below the gap in the slot 146, between the two edges of theanterior portion 206 (FIG. 19). However, the decayed bone at that areamay simply fall from the peripheral bone without requiring an additionalcut. Once the bone is completely removed from within the cut area formedby the osteotomes, a cavity that corresponds to the tibial augment beinginserted therein should result.

After forming the cavity, which alternatively could be formed using therasp technique mentioned earlier, as well as by other known techniques,the provisional augment 90 (FIG. 9) may be temporarily implanted todetermine whether the cavity is properly sized, or if additional boneneeds to be removed. The provisional may be inserted either with the aidof one of the holders 110 or 111 (FIGS. 10 and 12) or by using one ofthe pushers 130 (FIG. 14), or with a combination of both a holder and apusher. At this point, the provisional 90 may also be used to trial thelocations of the tibial base plate provisionals (or the provisionals ofthe tibial tray and stem). After the fit is adequately tested with theprovisional 90, it can be removed by using the provisional holder 110 or111 in the manner previously described. Then, the permanent tibialaugment, such as augment 10 of FIG. 1, is inserted using the pusher 130(FIG. 12). After properly seating the augment within the cavity, cementis applied to the proximal surface 12 of the augment, and the stemmedtibial base plate 102 (FIG. 8) is attached to the augment and to theperipheral bone remaining around the cavity. Then, the remainder of theknee joint prosthesis 100 is attached using any desired method, and thesurgical procedure continues in the customary manner.

While various embodiments of the present invention have been shown anddescribed, it should be understood that other modifications,substitutions and alternatives may be apparent to one of ordinary skillin the art. Such modifications, substitutions and alternatives can bemade without departing from the spirit and scope of the invention, whichshould be determined from the appended claims.

Various features of the invention are set forth in the appended claims.

What is claimed is:
 1. A method for augmenting a tibial component of a knee joint prosthesis, comprising: implanting a tibial component of a knee joint prosthesis, a first annular member, and a second annular member in a proximal portion of a human tibia, wherein the tibial component, the first annular member, and the second annular member are left in the proximal portion of the human tibia with the first annular member and the second annular member connected to the tibial component for augmenting the tibial component in the proximal portion of the human tibia, wherein the tibial component comprises a tibial plate and a tibial stem component extending from said tibial plate, wherein the first annular member and the second annular member are of different sizes and each include a proximal end, a distal end, and a tapered outer surface that tapers in a direction toward the distal end of the respective annular member, wherein the first annular member and the second annular member are each constructed separately from said tibial component for subsequent connection to said tibial component, wherein said first annular member and said second annular member prior to connection to said tibial component each have an established size and shape for implantation in the human tibia, wherein said first annular member and said second annular member are each formed with a porous metal material for facilitating bony ingrowth into said first annular member and said second annular member, and wherein said first annular member and said second annular member each provide a passageway extending entirely through the respective annular member, and wherein the tibial component being connected to the first annular member and the second annular member in the proximal portion of the human tibia includes the first annular member and the second annular member being in a stacked arrangement in a proximal-distal direction in the proximal portion of the human tibia with the tibial stem component received in the passageways of the respective annular members.
 2. The method of claim 1, wherein said established size and shape of at least one of the first annular member and the second annular member fills an existing cavitary defect within the proximal portion of the human tibia.
 3. The method of claim 1, wherein said established size and shape of at least one of the first annular member and the second annular member fills a cavity prepared in the proximal portion of the human tibia.
 4. The method of claim 1, wherein said established size and shape of at least one of the first annular member and the second annular member includes the respective annular member having a medial-lateral dimension of 59 mm at the proximal end of the respective annular member.
 5. The method of claim 1, wherein the first annular member and the second annular member are implanted in the proximal portion of the human tibia before the tibial stem component is received in said respective passageways.
 6. The method of claim 1, wherein said first annular member and said second annular member are formed with a tantalum-based porous material.
 7. The method of claim 1, wherein at least one of said first annular member and said second annular member has a height of at least 15 mm but no more than 30 mm extending between the proximal end and the distal end of the respective annular member.
 8. The method of claim 1, wherein the respective passageway of at least one of the first annular member and the second annular member is tapered.
 9. The method of claim 1, wherein said stacked arrangement creates extensions of outer lateral, medial, posterior, and anterior surfaces of said first annular member and said second annular member.
 10. The method of claim 1, wherein a majority of at least one of the first annular member and the second annular member is of a uniform wall thickness.
 11. The method of claim 1, wherein at least one of the first annular member and the second annular member includes a reduced thickness wall portion.
 12. The method of claim 1, wherein at least one of the first annular member and the second annular member has a medial-lateral width of said proximal end of the respective annular member that is greater than a medial-lateral width of said distal end of the respective annular member.
 13. The method of claim 1, wherein at least one of the first annular member and the second annular member has an anterior-posterior width of said proximal end of the respective annular member that is greater than an anterior-posterior width of said distal end of the respective annular member. 